Solid stabilized hydrazinium diperchlorate propellant

ABSTRACT

A SOLID PROPELLANT HAVING HYDRAZINIUM DIPERCHLORATE AS THE OXIDIZER IN A HYDROCARBON FUEL BINDER CONTAINS A STABILIZING AMOUNT OF A CHELATING AGENT FOT STABILIZATION WITH RESPECT TO VIBRATIONAL AND THERMAL SHOCK. ALSO INCLUDED ARE VARIOUS PROPELLANT ADJUVANTS FOR ADDITIONAL PERFORMING CHARACTERISTICS.

United States Patent Int. Cl. C0611 5/06 US. Cl. 149-19 17 ClaimsABSTRACT OF THE DISCLOSURE A solid propellant having hydraziniumdiperchlorate as the oxidizer in a hydrocarbon fuel binder contains astabilizing amount of a chelating agent for stabilization with respectto vibrational and thermal shock. Also included are various propellantadjuvants for additional performing characteristics.

This invention concerns stabilized oxidizer compositions and theirpreparation.

More particularly, thi invention relates to the preparation ofstabilized hydrazinuim diperchlorate oxidizer composition using smaquantities of metal chelating agents as the stabilizing agents.

Hydrazinium diperchlorate (HP is an exceeding energetic oxidizer. Inaddition to its potency, it has certain other advantages which wouldmake it a desirable oxidizer component in solid propellant compositions.These advantages include high density and a high burning rate. Inaddition, the composition is available in large quantities in a highstate of purity at relatively moderate cost. The high density of HPpermits high loading levels compared to many less energetic oxidizers.This in turn increases the available energy of the propellantcomposition on a unit weight basis and increases the potential range ofthe rocket hardware. All of these attributes of HP are importantconsiderations in military and aerospace operations.

Unfortunately, HP has an important defect which has curtailed itswidespread use. This shortcoming is its relatively poor stability tovibrational and thermal shock especially when formulated with the usualpolymeric fuel binder and propellant adjuvants. While the oxidizer canbe prepared by a number of processes, including neutralization andmetatheses, the HP product obtained is sensitive to thermal ormechanical shock, i.e., shock can induce its decomposition, which canproceed either as a defiagration or a detonation.

Because of its poor shock sensitivity, in the present state of the art,extreme care must be used in the storage, handling, and formulation ofHP -based propellants. In fact the poor sensitivity of HP presentlylimits the size of the batches of HP based propellant and presentlyrestricts its use solely to experimental purposes.

In view of the potential value of HP as a propellant oxidizer andbecause of its relatively high sensitivity, a need exists for a methodof preparing HP compositions stable toward mechanical and thermal shock.A desirable method would decrease the mechanical and thermal sensitivityof HP severalfold, would utilize readily available and inexpensivestabilizers and could be utilized by relatively unskilled personnelwithout the need for special 3,698,969 Patented Oct. 17, 1972 iceequipment. Ideally the stabilizer could be used in sufficiently smallquantities so that the potential energy of the oxidizer would not beappreciably diminished. A stabilizing process possessing theseadvantages would represent a substantial advance in the propellant art.

7 It is therefore an object of this invention to prepare hydraziniumdiperchlorate compositions having improved stability to detonation byvibrational and thermal shock.

It is a further object of this invention to develop a process forpreparing the above compositions inexpensively, from readily availablematerials without the need for special techniques or equipment.

Yet a further object of this invention is the preparation of HP basedpropellant compositions stabilized toward mechanical and vibrationalshock.

Additional objects will become apparent to the reader after a perusal ofthis application.

In practice, a stabilizing quantity of a stabilizing agent is contactedwith HP product or its aqueous or nonaqueous solutions until ahomogenous stabilized HP composition is produced.

In the preferred practice, about 0.1 to 10% by weight ofethylene-diaminetetraacetic acid (EDTA) is added to a reaction mixturecontaining HP prior to the final crystallization which precedes thefinal drying step.

The term stabilizing agent as used throughout this application refers tothat quantity of stabilizer required to substantially improve thesensitivity of HP to detonation by thermal or vibrational shock. Thequantity of stabilizer required varies according to the particularstabilizer used. However in most instances the amount of stabilizerrequired varies between 0.01 to 10.0% by weight of the HP treated.

The stabilizers of this invention are of diverse origin and structure.For this reason they cannot be described structurally. However,interestingly enough, all of the stabilizers appear to have the abilityto form soluble complexes with metallic ions and are referred to in theart as chelating agents. In addition to the preferredethylenediaminetetraacetic acid and its salts, the following chelatingagents can be used: polycarboxylic acids such as malonic acid,ethylmalonic acid, nitrilotriacetic acid, amines such asethylenediamine, N,N-dimethylethylenediamine, diethylenetriamine, 1,2,3triaminopropane, bipyridyl, amino acids and peptides such as alanine,glycine, aspargan, methionine, valine, aminoethylphosphonic acid,

'ethylenediamine N,N diacetic acid, ethylenediaminetetrapropionic acid,hydroxy acids such as salicylic acid, sulfosalicylic acid, hydroxyaldehydes such as salicylaldehyde and its alkoxy, halo and alkylderivatives, B ketones such as benzoylacetone, acetylacetone,thenoyltrifiuoroacetone, phenolics such as 8 hydroxyquinoline,3,5-disulfopyrocatechol among many others.

To set forth the advantages and working of this invention in thegreatest possible detail the following illustrative embodiments aresubmitted.

In one embodiment, a sample of hydrazinium diperchlorate in a by weightperchloric acid mother liquor (produced in a neutralization of aqueoushydrazine with concentrated (72% by weight) perchloric acid), is dividedinto two equal portions. To one stirred portion is added 8% by weight(of the HP of ethylenediaminetetraacetic acid. After 15 minutes ofstirring, the treated solution is cooled to l0 C. and the precipitatedhydrazinium diperchlorate filtered off. After drying under vacuum for 15hours a propellant grade HP product is obtained.

The second portion of the hydrazinium diperchlorate in perchloric acidis processed as above except that no treatment with ethylene diaminetetraacetate acid is given before cooling, precipitation and vacuumdrying of the final product.

The treated product and untreated product separately are each admixedwith separate portions of CP grade iron powder amounting to 1.3% of itsweight and heated to 120 C. in a sealed Pyrex glass tube. After 11minutes the untreated sample of product decomposes. The EDTA treatedsample decomposes after about 53 minutes. This approximately 5 folddecrease in thermal stability is both significant and unexpected. Alarge decrease in sensitivity toward shock between the two samples isalso observed.

In another embodiment, the anhydrous HP' derived from a metatheticalpreparation is divided into two parts. The first part is treated with 8%its weight of EDTA and vacuum dried. The second part is untreated anddried under the same vacuum conditions. Again each portion is treatedwith about 2% its weight of CP 100 mesh iron powder. Both samples areheated to 125 C. The same order of decreased sensitivity toward thermalshock is observed.

In a further embodiment a 15 parts by weight sample of CP anhydrous,hydrazinium diperchlorate in 100 parts by weight of 72% by Weightperchloric acid is treated with 1.5 parts by weight of nitrilotriaceticacid. The mixture is stirred for 15 minutes cooled to 10 C. andfiltered. The filter cake is dried for 6- hours under 5 mm./Hg. Asubstantial decrease in sensitivity toward detonation from vibration andthermal shock is noted compared to untreated control material.

In a further embodiment a 15 parts by weight sample of CP anhydrous,hydrazinium diperchlorate in 100 parts by weight of 72% by weightperchloric acid is treated 1.5 parts by weight of methionine. Themixture is stirred for 15 minutes cooled to -10 C. and filtered. Thefilter cake is dried for 16 hours under 5 mm./ Hg. A substantialdecrease in sensitivity toward detonation from vibration and thermalshock is noted compared to untreated control material.

In a further embodiment a 15 parts by weight sample of CP anhydrous,hydrazinium diperchlorate in 100 parts by weight of 72% by weightperchloric acid is treated with 1.5 parts by weight ofethylenediaminetetrapropionic acid. The mixture is stirred for 15minutes cooled to 10 C. and filtered. The filter cake is dried for 18hours under 5 mm./Hg. A substantial decrease in sensitivity towarddetonation from vibration and thermal shock is noted compared tountreated control material.

In a further embodiment a 15 parts by Weight sample of CP anhydrous,hydrazinium diperchlorate in 100 parts by weight of 72% by weightperchloric acid is treated with 1.5 parts by weight of8-hydroxyquinoline. The mixture is stirred for 15 minutes cooled to -10C. and filtered. The filter cake is dried for 6 hours under 5 mm./Hg. Asubstantial decrease in sensitivity toward detonation from vibration andthermal shock is noted compared to untreated control material.

In a further embodiment a 15 parts by weight sample of CP anhydrous,hydrazinium diperchlorate in 100 parts by weight of 72% by weightperchloric acid is treated with 1.5 parts by weight of sodiumtripolyphosphate. The mixture is stirred for 15 minutes cooled to --l C.and filtered. The filter cake is dried for 14 hours under mm./ Hg. Asubstantial decrease in sensitivity toward detonation from vibration andthermal shock is noted compared to untreated control material.

In a further embodiment a 15 parts by weight sample of CP anhydrous,hydrazinium diperchlorate in 100 parts by weight of 72% by weightperchloric acid is treated with 1.5 parts by weight of salicylic acid.The mixture is stirred for 15 minutes cooled to C. and filtered. Thefilter cake is dried for 16 hours under 5 mm./ Hg. A substantialdecrease in sensitivity toward detonation from vibration and thermalshock is noted compared to untreated control material.

. In further embodiments, a substantial decrease in sensitivity towarddetonation from thermal shock is observed when 5 parts by weight samplesof CP grade anhydrous hydrazinium diperchlorate are treated with 0.5part by weight of the following chelating agents and vacuum dried.

CHELATING AGENTS APPLIED Malonic acid Sulfosalicylic acid GlycineBenzoylacetone Asparagine Thenoyltrifluoroacetone Valine 3,5-disulfopyrocatechol The stabilized hydrazinium diperchlorate of thisinvention can be formulated With the usual propellant components to formthe finished propellant composition. The components include in additionto the stabilized HP; of this invention, the components shown below inthe proportions indicated.

(1) 10 to 40 parts by weight of a combustible fuel binder, (2) 0 to 25parts by weight of propellant adjuvants.

The components are admixed until a homogenous mixture is produced thenloaded into a rocket motor for curing to the desired physical state. Adescription of these propellant components is given below.

Binders The binders that can be used with the stabilized HP of thisinvention are saturated and unsaturated hydrocarbon polymers. A flavoredgroup are the polyalkyldieues containing reactive sites such as hydroxy,carboxy, carbonyl, epoxy, amino, imino, and the like. Most of thesepolymers are commercially available products or can be made using knownpolymerization procedures. For example, polyalkadienes containingcarboxyl groups can be prepared by polymerizing or reacting manymaterials including conjugated dienes containing from 4 to 8 carbonatoms. These include 1,3-butadiene, isoprene, piperylene,methylpentadiene, 2-ethyl-l,3-butadiene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene among others. In addition,conjugated dienes containing reactive substituents along the chain canalso be employed, such as for example, halogenated dienes, such aschloroprene, fluoroprene, etc. Of the conjugated dienes, the preferredmaterial is butadiene, with isoprene and piperylene also beingespecially suitable. In addition to the conjugated dienes, othermonomers which can be employed are aryl-substituted olefins, such asstyrene, various alkyl styrenes, paramethoxystyrene, vinylnaphthalene,vinyltoluene, and the like; heterocyclic nitrogen containing monomers,such as pyridine and quinoline derivatives containing at least 1 vinylor alphamethylvinyl group, such as 2-vinylpyridine, 3-vinylpyridine,4-vinylpyridine, 3-ethyl-5-vinylpyridine, 2- methyl-S-vinylpyridine,3,S-diethyl-4-vinylpyridine, etc. In addition, monoand disubstitutedalkenyl pyridines and the like quinolines; acrylic acid esters, such asmethyl acrylate, ethyl acrylate; alkacrylic acid esters, such as methylmethacrylate, ethyl methacrylate, propyl methacrylate, butylmethacrylate, methyl vinyl ether, vinyl chloride, vinylidene chloride,vinylfuran, vinylcarbazole, vinylacetylene, etc., can be used as polymersubstrates.

The above compounds, in addition to being polymerizable alone, are alsocopolymerizable with each other and may be copolymerized to formterminally reactive polymers. In addition, copolymers can be prepared,using minor amounts of copolymerizable monomers containing more than onevinylidene group such as 2,4-divinylpyridine, divinylbenzene,2,3-divinylpyridine, 3,5-divinylpyridine, 3,5-divinylpyridine,2,4-divinyl-6-methylpyridine, 2,3-divinyl-5-ethylpyridine, and the like.

Another group of superior binders are the saturated binders containingfree carboxyl sites. These binders,

which are the condensates of saturated glycols and saturated acids, areadvantageous in certain respects compared to the correspondingpolyalkadiene binders. For example, they are more energetic on a weightbasis and they are more compatible with HP because they do not containunsaturated carbon to carbon bonds. A specific saturated binder which isfavored is the condensate of neopentyl glycol and Emery 3389 (aproprietary dimer acid condensation polymer sold by Emery Industries);also favored are the halogenated saturated binders such as the carboxylcontaining flouroalkanes, and carboxyl terminated alkane polymers suchas carboxyl terminated polyisoprene.

The polymeric fuel binders of this invention can range in molecularweight from 250l2,000 or more, although the most satisfactory resultshave been obtained using carboxyl terminated hydrocarbon polymersranging in molecular weight between 500-6,000. As indicated, especiallyfavored are the carboxyl terminated polybutadienes and the neopentylglycol condensate of that molecular weight range.

Propellant adjuvants In addition to the curing agents, accelerators,polymerization and vulcanization catalysts and the like which areincluded within the fuel binder content of the inventive propellantcompositions, certain additives, ignition catalysts, conditioning ormodifying agents, surfactants, high energy metals, their 'hydrides andthe like can often be advantageously added to the propellantcompositions to alter or improve their physical and combustioncharacteristics. For convenience sake, these substances are hereingenerically referred to as propellant adjuvants and they can be presentin the finished propellant composition in amounts up to about 30 partsby weight down to part by weight of the final propellant composition.

More commonly, however, the adjuvants comprise from about 20 parts byweight or even less down to about parts by weight of propellantcompositions. Among the many propellant adjuvants which can be used areincluded the following typical materials. Plasticizers such as thealkylphthalates and the like, darkening agents such as carbon black orlamp black, ballistic agents such as potassium sulfate, hygroscopicityinhibitors, such as dinitro-toluene and various coolants, combustion andburning rate catalysts. The combustion catalysts are of diversestructure but generally are compounds containing oxygen. These catalystscan be inorganic or organic compounds. They include, among many others,such as ferrous, ferric, magnesium, titanium, calcium, molybdenum, andvanadium oxides and the like. Especially effective as combustioncatalysts are the chromates and dichromates, generally with ammoniumdichromate being a preferred catalyst. Organics such as nitrocellulosecan also be effectively used.

A favored group of adjuvants are the finely divided lightweight and highenergy metals and nonmetals such as aluminum, beryllium, boron, siliconand the like. These materials can be used by themselves, as theircarbides and hydrides, or they can be employed in the form of theirpolymer coated particles.

To demonstrate the preparation of typical HP based propellantsstabilized toward vibrational and thermal shock the followingembodiments is submitted.

In one illustrative embodiment of this invention, the followingpropellant components are blended in an appropriately'sized mixingvessel equipped with an efiicient means of blending, cooling and heatingin the manner described.

To a stirred 13 parts by weight portion of commercially availablecarboxy terminated polybutadiene having a molecular weight range between500 and 6000. (Thiokol HC polymer) is added to 2 parts by weight ofl,1-ethylenebis(2-ethyl)aziridine curing agent and 16 parts by weightdegreased aluminum powder (having a particle size between 3 and 30microns). After the mixture appears to be uniform, a 70 parts by weightportion of stabilized anhydrous propellant grade hydraziniumdiperchlorate previously treated by 10% its weight ofethylenediaminetetraacetic acid is blended in. The blending and mixingoperation is cotninued for an additional 30-90 minutes and is cast intoa /2 lb. rocket engine casing. The propellant is cured at 135 F. for 96hours. The cured propellant had good flexibility and Shore A hardness.

As indicated earlier this invention is advantageous in both its processand composition aspects.

In its process aspects this invention permits the stabilization of HPtoward thermal and vibrational shock by the incorporation of a smallquantity of an inexpensive stabilizer to the I-IP prior to use. Nospecial application equipment or techniques are required and the sourceof the HP is not important to success.

'In its compositional aspects, this invention permits the use of highlyenergetic propellant compositions than has previously been possible.Further, these compositions withstand handling and storage underoperational conditions with less hazard than was heretofore thoughtpossible.

As the above discussions and previous embodiments have indicatednumerous modifications and changes in this invention are possiblewithout departing from the inventive concept. The metes and bounds ofthis invention are best indicated by the claims which follow.

What is claimed is 1. A hydrazinium diperchlorate composition capable ofcuring to a solid and stabilized toward vibrational and thermal shockconsisting essentially of from .85 to 8.5 parts by weight of a metalchelating agent selected from the group consisting of:

Alkylenediamines Alkylenetriamines Polycarboxyl'ic acidsNitrilotriacetic acid Amino acids Peptides The acids and salts ofalkylenediamines and alkylenetriamines Hydroxy acids Hydroxy aldehydesB-ketones Phenolics, from about 10 to 40 parts by weight of acombustible polymeric hydrocarbon fuel binder including a curing agentin admixture therewith, and from about 45 to parts by weight ofhydrazinium diperchlorate.

2. The composition of claim 1 wherein the stabilizing agent isethylenediaminetetraacetic acid.

3. The composition of claim 1 wherein the stabilizing agent isnitrilotriacetic acid.

4. The composition of claim 1 wherein the stabilizing agent ismethionine.

5. The composition of claim 1 wherein the stabilizing agent isethylenediaminetetrapropionic acid.

6. The composition of claim 1 wherein the stabilizing agent is8-hydroxyquinoline.

7. The composition of claim 1 wherein the stabilizing agent is sodiumtripolyphosphate.

8. The composition of claim 1 wherein the stabilizing agent is salicylicacid.

9'. The composition of claim 1 wherein the stabilizing agent isbenzoyl-acetone.

10. The composition of claim 1 wherein the stabilizing agent isthenoyltrifluoroacetone.

11. The composition of claim 1 wherein the stabilizing agent is3,5-disulfopyrocatechol.

12. A hydrazinium diperchlorate based propellant composition capable ofcuring to a solid and stabilized toward vibrational and thermal shockconsisting of the following components in the proportions indicated.

(a) about 10 to 40 parts by weight of a combustible polymerichydrocarbon fuel binder including a curing agent in admixture therewith.

(b) about 45 to 85 parts by weight of hydrazinium diperchlora'te,

() about 0 to 25 parts by weight of propellant adjuvants,

(d) about .85 to 8.5 parts by Weight of a metal chelating agent.

13. A hydrazinium diperchlorate based propellant composition capable ofcuring to a solid and stabilized toward vibrational and thermal shockconsisting of:

(a) about to 40 parts by weight of a combustible polymeric hydrocarbonfuel binder including a curing agent in admixture therewith,

(b) about 45 to 85 parts by weight of hydrazinium diperchlorate,

(c) about 0 to 25 parts by weight of propellant ad- (a) the combustiblefuel binder is a carboxyl containing hydrocarbon resin, and

(b) the metal chelating agent is ethylenediaminetetraacetic acid.

15. The composition of claim 13 wherein (a) the combustible fuel binderis a carboxyl containing hydrocarbon resin, and

('b) the metal chelating agent is sodium tripolyphosphate.

16. The composition of claim 13 wherein (a) the combustible fuel binderis a carboxyl containing hydrocarbon resin, and

(b) the metal chelating agent is nitrilo'triacetic acid.

17. The composition of claim 13 wherein (a) the combustible fuel binderis a carboxyl containing hydrocarbon resin, and

(b) the metal chelating agent is methionine.

References Cited UNITED STATES PATENTS 3,006,743 10/1961 FOX et a1 l49363,130,096 4/1964 Pruitt et a1. 14919 3,155,552 11/1964 Vriesen l49 -19BENJAMIN R. PADGETT, Primary Examiner US. Cl. X.R.

